Situ recovery of petroleumlike hydrocarbons from underground formations

ABSTRACT

A void in a petroleumlike hydrocarbon-containing geological formation is filled with an acidic solution, and a nuclear device is exploded therein. The detonation fractures the surrounding shale structure, and the solution penetrates into the hydrocarbon shale in and about the resulting cavity, increasing its porosity and permeability. The desired hydrocarbon may then be removed by conventional methods, as by in situ retorting.

l 6 (3"3 07 o XR inventor Alvin Abrams Woodmere, Long Island, N.Y. Appl. No. 686,285 Filed Nov. 28, 1967 Patented Jan. 12, 1971 Assignee Irradiation Controls Inc.,

New York, N.Y.,

a corporation of New York SlTU RECOVERY OF PETROLEUMLIKE HYDROCARBONS FROM UNDERGROUND FORMATIONS 2 Claims, No Drawings US. Cl 166/247, 166/272, 166/307 Int. Cl E2lb 43/26, E21 b 43/27 Field of Search 166/36, 42,

[56] References Cited UNITED STATES PATENTS Re2 1 ,356 211940 Pitzer l66/42X 2,676,662 4/1954 Ritzmann 166/36 3,024,840 3/1962 Allen 166/1 1 3,113,620 12/1963 Hemminger.. 166/11 3,342,257 9/1967 Jacobs et al. l66/36X 3,404,919 10/1968 Dixon 166/36X Primary Examiner-Stephen J. Novosad A ttorney Davis, Hoxie, Faithfull and Hapgood SITU RECOVERY OF PETROLEUMLIKE HYDROCARBONS FROM UNDERGROUND FORMATIONS DISCLOSURE OF INVENTION This invention relates to an improvement in the recovery of gas, oil, and other petroleumlike hydrocarbon energy bearing compositions from subsurface shale or like formations and, more specifically, to a methodfor increasing the permeability and porosity of the shale or like strata to aid recovery of the hydrocarbons.

Hydrocarbon containing geological formations, e.g., oil containing shale, kerogen rock, or the like are relatively common, and are typically found beneath relatively thick overburden formation(s) of earth, cap rock or the like. Despite their relatively high incidence, extraction of the desired substances has been limited. I

One method for recovering the oil or other desired hydrocarbon is to mine the oil-containing shale, or kerogen rock. After transportation to a suitable refinery, the relatively compact rock material is first fractured to increase its rate of subjection to reaction. Oil is then recovered from the crushed shale, as by employing a retorting .operation such as is described in L. P. Evans U.S. Pat. No. 3,281,349 issued Oct. 25, i966. However, because of the requisite operations of mining, transporting, fracturing, and retorting theshale, and disposing of the overburden, such a mining technique is most often not economically competitive with alternative sources of the particular hydrocarbon. I

To obviate many of the difficulties associated with mining, in situ recovery of the oil, gas or other mineral has been suggested. Essentially this compriseseffecting an underground explosion to fracture the pertinent shale strata, thereby coincidentally creating a cavity about the fractured shale to serve for underground retorting. Recently, the use of nuclear devices has been contemplated for the requisite explosive. After such explosion(s), the desired hydrocarbon is removed by any one of several known methods. For example, the hydrocarbon may be removed via an outlet conduit responsive to heated gas, brine, or the like being drivenunder pressure into the cavity via an inlet conduit. Alternatively, an ignited combustible gas may be driven down the inlet conduit.

However, the above and other in situ processes will efficiently recover the desired hydrocarbon only from the shale structure which has been increased in permeability and porosity responsive to the nuclear explosion(s). More specifically, the retorting or other product extraction process can operate only on the exposed surfaces and fissures in the fractured shale which has such characteristics. For prior art explosion methods, this is limited to the shale directly fractured by the nuclear or other explosive device, and the shale structure immediately surrounding the resulting cavity. Accordingly, a relatively limited amount of useful shale structure is prepared by each explosion. 1

1 It is therefore an object of the present invention to provide.

an improved method for removing hydrocarbons from subsurface geological deposits.

More specifically, it is an object of the present invention to increase the permeability and porosity of hydrocarbon energy containing shale or like formations such that a relatively large product recovery can be had responsive to each subsurface strata-fracturing explosion.

The above and other objects of the present invention are realized in an illustrative improvedmethod for the recovery of a desired hydrocarbon, e.g., oil, from subsurface formations. A void is created in the oil shale strata by any conventional method, for example by boring into the formation and exploding a conventional, or relatively small nuclear device at the bottom of such bore. The depth of the void is determined by the thickness and density of the overburden, and by the thickness of the oil shale formation.

The bore hole is redrilled into the void and a second nuclear explosive inserted therein. The void is then filled. either in toto or to a substantial degree, with a liquid. preferably serving as a carrier for selected additives. As discussed hereinafter, an acidic water solution may be employed.

The nuclear device is exploded to produce a subsurface cavity substantially larger than the initial void. The cavity includes therein a great amount of oil shale, kerogen rock or the like which was fractured by the second explosion, and which is thus characterized by many crevices and fissures, thereby exhibiting a relatively high permeability and porosity.

In addition, the oil shale structure surrounding the cavity is also characterized by an increased permeability and porosity. These characteristics are imparted by the blast directly, and substantially magnified in scope by the penetration of the acid solution into the shale structure. The acid attacks the shale, decomposing a portion thereof, and also causing apertures and fissures therein to effect the desired increased characteristics.

The relevant substance, i.e., the oil contained within the shale formation, is extracted by any prior'art method. For example, inlet and outlet conduits may be drilled into the cavity and heated gases, steam, brine or the like may be driven into the cavity to effect underground retorting in the known manner to drive the oil fraction out of the cavity via the outlet conduit. Since more of the oil-containing structure is made porous in accordance with the principles of the present invention, an increased hydrocarbon yield will result from any given size explosion.

It is noted at this point that the water or other liquid will absorb and moderate the principal radioactive byproducts of the nuclear explosion. Accordingly, the radioactivity of the resulting oil or other desired product is maintained at a relatively low level. Further, the vaporized liquid may be recovered in part after the explosion to comprise a commercially salable chemical product.

Also, additional additives may be included in the aqueous or other solution for special purposes and effects. For example, catalyst(s) to aid in the recovery process-may be employed. Also, additives which attach the shale formation to generate a retort aiding gas pressure may be utilized. 1

In addition, the above-described process may be repeated several times to continuously enlarge the cavity, with additional prepared shale material being produced with each explosion. i

It is to be understood that the above-described method is only illustrative of the principles of the present invention. Numerous modifications and adaptions thereof may be readily devised by those skilled in the art without departing from the principles of the present invention. For example, in addition to oil shale or kerogen rock, the invention is applicable to tar sands, oil sands, bituminous limestone, peat and anthracite coal formations, and the like.

1. An improved method for extracting petroleumlike hydrocarbons from subsurface rocklike formations including the steps of forming a void space in the hydrocarbon-containing rock formation, inserting a liquid state noncombustible aqueous acidic solution in said void space, inserting a nuclear device in said void space, and exploding said nuclear device in said liquid containing void, said liquid being operative for absorbing radioactive byproducts from said explosion step and for vaporizing and penetrating into the surrounding rocklike formation to increase the explosive effect of said nuclear explosion and, further, for increasing the hydrocarbon productive effect of said explosion by chemical action over an ex tended time period.

2. A method as in claim 1 further comprising the step of boring inlet and outlet conduits into. the cavity resulting from said nuclear explosion, and retorting the hydrocarbon-containing materials included in said cavity by inserting a heated, pressurized fluid in said inlet conduit and extracting said hydrocarbon from said outlet conduit. 

2. A method as in claim 1 further comprising the step of boring inlet and outlet conduits into the cavity resulting from said nuclear explosion, and retorting the hydrocarbon-containing materials included in said cavity by inserting a heated, pressurized fluid in said inlet conduit and extracting said hydrocarbon from said outlet conduit. 